I want to make a set of magic stealing jewelry, the proprietor of the jewelry sells it at a steep discount, but reaps a reward in the energy that the jewels harvest and return to him, the holder of the master jewel.
Life energy is cliche and won't last long, plus will draw all sorts of unpleasant PC attention.
I was thinking basically stealing mana/magic power/potential from those who wear it. Non magic users wouldn't notice a mana/energy drain since they are not attuned to it, but they would notice side effects of it's absents. Stuff like depression, lethargy, morose and morbid thoughts, or if an individual were more attuned to those darker energies they would be swing more towards the manic side of the pendulum.
What can I do to keep this from being cliche?